如何创建像 iOS 共享表菜单一样的短模式叠加？

Question

我正在尝试创建一个自定义的短菜单，从屏幕底部向上滑动并停留在底部（如 iOS 共享表）。我很难弄清楚如何去做。我尝试将视图控制器呈现为模态并设置首选内容大小，但它仍将其呈现为全屏。我怎样才能呈现一个简短的、类似模态的叠加层？

Answer 1

您可以使用 UIPresentationController 和 UIViewControllerTransitioningDelegate。

作为起点，这里有几行代码：

UIViewControllerTransitioningDelegate

class OverlayTransitioningDelegate: NSObject, UIViewControllerTransitioningDelegate {

    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
        return OverlayPresentationController(presentedViewController:presented, presenting:presenting)
    }

}

UIPresentationController

class OverlayPresentationController: UIPresentationController {

    private let dimmedBackgroundView = UIView()
    private let height: CGFloat = 200.0

    override init(presentedViewController: UIViewController, presenting presentingViewController: UIViewController?) {
        super.init(presentedViewController: presentedViewController, presenting: presentingViewController)
        let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(backgroundTapped))
        self.dimmedBackgroundView.addGestureRecognizer(tapGestureRecognizer)
    }

    override var frameOfPresentedViewInContainerView: CGRect {
        var frame =  CGRect.zero
        if let containerBounds = containerView?.bounds {
            frame = CGRect(x: 0,
                           y: containerBounds.height - height,
                           width: containerBounds.width,
                           height: height)
        }
        return frame
    }

    override func presentationTransitionWillBegin() {
        if let containerView = self.containerView, let coordinator = presentingViewController.transitionCoordinator {
            containerView.addSubview(self.dimmedBackgroundView)
            self.dimmedBackgroundView.backgroundColor = .black
            self.dimmedBackgroundView.frame = containerView.bounds
            self.dimmedBackgroundView.alpha = 0
            coordinator.animate(alongsideTransition: { _ in
                self.dimmedBackgroundView.alpha = 0.5
            }, completion: nil)
        }
    }

    override func dismissalTransitionDidEnd(_ completed: Bool) {
        self.dimmedBackgroundView.removeFromSuperview()
    }

    @objc private func backgroundTapped() {
       self.presentedViewController.dismiss(animated: true, completion: nil)
    }


}

怎么称呼

let overlayTransitioningDelegate = OverlayTransitioningDelegate()

@IBAction func onOpenModalOverlay(_ sender: Any) {
    let overlayVC = OverlayViewController()
    overlayVC.transitioningDelegate  = self.overlayTransitioningDelegate
    overlayVC.modalPresentationStyle = .custom
    self.present(overlayVC, animated: true, completion: nil)
}

演示

OverlayViewController 是一个普通的 ViewController。在这里，我使用了丑陋的绿色背景色，以便更容易识别叠加层。